The present invention relates to secondary carpet backings for adherence to the underside of a carpet material by an adhesive, and in particular to an improved secondary carpet backing which has improved adhesion characteristics.
As is known in the art, it is often desirable to apply secondary backings to the bottom surface or underside of a carpet material to add dimensional stability, weight and durability to the formed carpet structure. Such secondary backing materials have traditionally been made of woven jute. More recently, however, due to the difficulties in obtaining a reliable source of jute and its highly variable costs, manufacturers have sought to find a suitable replacement. One material that has many of the requisite physical properties for the secondary backing, and is available at a reasonable price, is woven synthetic scrim of the type that is commonly used for the primary carpet backing. Generally, both the warp-wise and weft-wise yarns of such woven backing structures are made of a synthetic material, such as for example, oriented polyolefin filaments which are woven in accordance with conventional weaving techniques to form the backing structure. However, because of the smooth, slippery and generally impervious nature of such polyolefin yarns, commercially available latex adhesives do not always form strong bonds between the synthetic yarn backing fabrics and the underside of the primary carpet material. It should be noted that such problems of adhesion are generally minimized when such synthetic yarns are used for the primary backings since such primary yarns generally have fiberous pile yarns piercing the primary backing which are highly receptive to the latex adhesives.
Various techniques have been employed in the past to improve the adhesion characteristics of such secondary carpet backings utilizing synthetic yarns or materials. For example, one technique which is quite common is to employ spun yarns made of synthetic fibers as the fill or weft-wise yarns in the woven secondary carpet backing. Such spun yarns are made from a multitude of relatively short fibers which are spun together to produce a synthetic yarn having a "hairy" appearance. These spun yarns may then be woven together with synthetic warp yarns which may comprise flat ribbons or tapes of synthetic material. For instance, one such typical woven structure is produced utilizing a leno weave process in which the warp yarns are arranged in pairs and woven in a manner so that the pairs of warp yarns are twisted between each weft yarn. As a result of the hairy construction of the weft yarns, improved adhesion of the adhesive for adhering the secondary backing to the primary backing is achieved.
Another similar technique for improving the adhesion characteristics has been the employment of heavily fibrillated yarns having a multitude of fibrils or splinters therealong as the weft or fill yarns in woven secondary backing constructions (see for example U.S. Pat. Nos. 3,542,632 and 4,145,467). In these techniques, it is contemplated that the latex adhesives will more readily adhere to the created fibrils or splinters.
A still further technique which has been employed in an attempt to improve the delamination or peel resistance characteristics of secondary carpet backings is disclosed in U.S. Pat. No. 3,817,817. In accordance with the method of that patent, a layer of staple fibers is needled onto the bottom surface of the scrim or secondary backing with portions of the fibers projecting through the top surface of the secondary carpet backing to provide a product which has the appearance of being jute and to which the latex adhesive can readily adhere or attach.
As can be appreciated, however, each of these prior art techniques requires the use of special types of filaments or the treating of same which are then utilized in forming a woven fabric structure. Also, because the filaments had to be specially treated prior to the weaving operation or subsequent thereto, it will be appreciated that such prior art techniques serve to significantly increase the cost of the resulting secondary carpet backing structure.
It is important to note in this regard that all of the secondary carpet backings of the prior art have generally comprised fabric structures which are woven from filaments of synthetic material. While knitted arrangements or fabric structures have been utilized for the primary carpet backings (see for example U.S. Pat. No. 3,732,708), secondary carpet backings have not previously employed weft inserted knit structures, possibly because of the relatively high denier filaments which are required in secondary carpet backing applications for providing the necessary strength, weight and durability and the fact that it has not previously been realized that improved adhesion characteristics can be achieved therewith.